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RuO<sub>2</sub> nanocluster as a 4-in-1 electrocatalyst for hydrogen and oxygen electrochemistry
Park, Han-Saem,Yang, Juchan,Cho, Min Kyung,Lee, Yeongdae,Cho, Seonghun,Yim, Sung-Dae,Kim, Byeong-Su,Jang, Jong Hyun,Song, Hyun-Kon unknown 2019 Nano energy Vol.55 No.-
<P><B>Abstract</B></P> <P>Partially hydrous RuO<SUB>2</SUB> nanocluster embedded in a carbon matrix (<I>x</I>-RuO<SUB>2</SUB>@C with <I>x</I> = hydration degree = <I>0.27</I> or <I>0.27</I>@C) is presented as a bifunctional catalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) for water splitting. Symmetric water electrolyzers based on <I>0.27</I>-RuO<SUB>2</SUB>@C for both electrodes showed smaller potential gaps between HER and OER at pH 0, pH 14 and even pH 7 than conventional asymmetric electrolyzers based on two different catalysts (Pt/C || Ir/C) that have been known as the best catalysts for HER and OER respectively. Moreover, <I>0.27</I>-RuO<SUB>2</SUB>@C showed another bifunctional electroactivity for fuel cell electrochemistry involving hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) that are the backward reactions of HER and OER respectively. Pt-level HOR electroactivity was obtained from <I>0.27</I>-RuO<SUB>2</SUB>@C, while its ORR activity was inferior to that of Pt with 200 mV higher overpotential required. The tetra-functionality of <I>0.27</I>-RuO<SUB>2</SUB>@C showed the possibility of realizing single-catalyst regenerative fuel cells.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We report a partially hydrous RuO<SUB>2</SUB> nanocluster embedded in a carbon matrix (<I>0.27</I>-RuO<SUB>2</SUB>@C) as a 4-in-1 electrocatalyst. </LI> <LI> <I>0.27</I>-RuO<SUB>2</SUB>@C shows an excellent water-splitting performance at pH 0, pH 14 and even pH 7. </LI> <LI> Also, it drives Pt-level hydrogen oxidation as well as fairly good oxygen reduction. </LI> <LI> Moreover, the tetra-functionality of <I>0.27</I>-RuO<SUB>2</SUB>@C shows the possibility of realizing single-catalyst regenerative fuel cells. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
A New α-Amylase from Reticulitermes speratus KMT1
Han Saem Park,Young Seok Ham,Hee Hoon Ahn,Keum Shin,Yeong Suk Kim,Tae Jong Kim 한국목재공학회 2014 목재공학 Vol.42 No.2
Termites are wood pests that cause vast economic damage every year. They digest both cellulose and starch, but the enzymes for starch digestion have not been well characterized. We obtained complete amino acid sequence information on the KME1 α-amylase from Reticulitermes speratus KMT1 through analysis of total mRNA sequences. The KME1 enzyme has two α-amylase domains and is 68% identical to the α-amylase from Blattellager manica, its closest rela-tivein the GenBank database. Some unique features of its conserved region and its distant evolutionary relationship to other insect α-amylases suggest that KME1 is a new type of α-amylase.
Park, Han-Saem,Yoo, Si-Ho,Cho, Sung-Bae Taylor Francis 2007 International journal of computer mathematics Vol.84 No.5
<P> The development of DNA microarray technology has facilitated in-depth research into cancer classification, and has made it possible to process thousands of genes simultaneously. Since not all genes are crucial for classifying cancer, it is necessary to select informative genes which are associated with cancer. Many gene selection methods have been investigated, but none is perfect. In this paper we investigate methods of finding optimal informative genes for classification of gene expression profiles. We propose a new gene selection method based on the forward selection method with regression analysis in order to find informative genes which predict cancer. The genes selected by this method tend to have information about the cancer that does not overlap with the other genes selected. We have measured the sensitivity, specificity, and recognition rate of the selected genes with the $k$-nearest-neighbour classifier for the colon cancer dataset and the lymphoma dataset. In most cases, the proposed method produces better results than gene selection based on other feature selection methods, yielding a high accuracy of 90.3% for the colon cancer dataset and 72% for the lymphoma dataset.</P>
Park, Han-Saem,Kim, Tae-Hee,Lee, Myeong-Hee,Song, Hyun-Kon The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.38
<P>Herein, we report on catalytic effects of transition metals (Me) in phospho-olivines (LiMePO<SUB>4</SUB>) on carbonization of cetyltrimethylammonium bromide (CTAB). Carbon coating is the required process to enhance electronic conductivity of phospho-olivines that are used as cathode materials for lithium ion batteries. Primary particles of phospho-olivines were <I>in situ</I> coated with CTAB and the adsorbed carbon precursor was carbonized to provide an electrically conductive pathway. CTAB was successfully carbonized in a significant amount with Fe in phospho-olivines (LiFe<SUB><I>x</I></SUB>Mn<SUB>1−<I>x</I></SUB>PO<SUB>4</SUB> with <I>x</I> = 1 and 0.5) even if CTAB is thermally decomposed around 300 °C without any residual mass in the absence of the phospho-olivines. LiMnPO<SUB>4</SUB> was the most inferior in terms of CTAB adsorption and thermal carbonization. LiNiPO<SUB>4</SUB> and LiCoPO<SUB>4</SUB> showed inefficient conversion of adsorbed CTAB to carbon even if their adsorption ability for CTAB is quite large. Also, the effect of the amount of carbon coating on LiFePO<SUB>4</SUB> was investigated, leading to a conclusion that the carbon thickness balanced between electronic and ionic conductances results in the best electrochemical performances of lithium ion batteries specifically at high discharge rates.</P> <P>Graphic Abstract</P><P>The transition metal in LiFePO<SUB>4</SUB> olivine materials transforms an uncarbonizable compound into a carbon coating on its surface. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2jm33841f'> </P>
Ca<SUP>2</SUP>-activated K<SUP></SUP> Currents of Pancreatic Duct Cells in Guinea-pig
Han-Wook Lee,Jingchao Li,Na-Youn Koo,Zheng Gen Piao,Sung Min Hwang,Jae-Woong Han,Han-Saem Choi,Jong-Heun Lee,Joong Soo Kim,Kyungpyo Park 대한생리학회-대한약리학회 2004 The Korean Journal of Physiology & Pharmacology Vol.8 No.6
There are numerous studies on transepithelial transports in duct cells including Cl<SUP></SUP> and/or HCO<SUB>3</SUB><SUP></SUP>. However, studies on transepithelial K<SUP></SUP> transport of normal duct cells in exocrine glands are scarce. In the present study, we examined the characteristics of K<SUP></SUP> currents in single duct cells isolated from guinea pig pancreas, using a whole-cell patch clamp technique. Both Cl<SUP></SUP> and K<SUP></SUP> conductance were found with KCl rich pipette solutions. When the bath solution was changed to low Cl<SUP></SUP>, reversal potentials shifted to the negative side, 75⁑4 mV, suggesting that this current is dominantly selective to K<SUP></SUP>. We then characterized this outward rectifying K<SUP></SUP> current and examined its Ca<SUP>2</SUP> dependency. The K<SUP></SUP> currents were activated by intracellular Ca<SUP>2</SUP>. 100 nM or 500 nM Ca<SUP>2</SUP> in pipette significantly (P<0.05) increased outward currents (currents were normalized, 76.8⁑7.9 pA, n=4 or 107.9⁑35.5 pA, n=6) at 100 mV membrane potential, compared to those with 0 nM Ca<SUP>2</SUP> in pipette (27.8⁑3.7 pA, n=6). We next examined whether this K<SUP></SUP> current, recorded with 100 nM Ca<SUP>2</SUP> in pipette, was inhibited by various inhibitors, including Ba<SUP>2</SUP>, TEA and iberiotoxin. The currents were inhibited by 40.4⁑% (n=3), 87.0⁑% (n=5) and 82.5⁑% (n=9) by 1 mM Ba<SUP>2</SUP>, 5 mM TEA and 100 nM iberiotoxin, respectively. Particularly, an almost complete inhibition of the current by 100 nM iberiotoxin further confirmed that this current was activated by intracellular Ca<SUP>2</SUP>. The K<SUP></SUP> current may play a role in secretory process, since recycling of K<SUP></SUP> is critical for the initiation and sustaining of Cl<SUP></SUP> or HCO<SUB>3</SUB><SUP></SUP> secretion in these cells.
동적 베이지안 네트워크를 이용한 모바일 라이프로그 기반 사용자 행동 예측
박한샘 ( Han-saem Park ),조성배 ( Sung-bae Cho ) 한국정보처리학회 2008 한국정보처리학회 학술대회논문집 Vol.15 No.2
개인화 장비 기술의 발달과 함께 최근 모바일 디바이스는 카메라, MP3 플레이어 등 다양한 기능을 포함하고 있으며, 많은 사용자가 이를 사용하고 있다. 모바일 디바이스는 사용자가 항상 휴대하기 때문에 사용자 정보를 습득하기에 유용하며 따라서 이로부터 수집된 다양한 정보를 바탕으로 최근 여러가지 서비스를 제공하기 위한 노력이 이루어지고 있다. 본 논문에서는 사용자의 모바일 로그를 바탕으로 행동 패턴을 파악하여 사용자가 앞으로 취할 행동을 예측하고자 하며, 이 과정에서 다양한 행동 패턴 중 정확한 행동 예측을 수행하기 위해 다음과 같은 방법을 활용하였다. 장소, 시간, 요일 정보를 함께 사용하여 동적 베이지안 네트워크를 이용해 시간 변화에 따른 사용자 행동 패턴을 학습하였으며, 개인 사용자 모델과 전체 사용자 모델을 따로 학습함으로써 더 정확한 행동 패턴의 학습이 가능하도록 하였다. 실험을 위해 대학생들로부터 수집된 모바일 로그를 통해 제안하는 행동 예측 모델의 성능을 확인한 결과 77~94%의 예측 정확도를 보임을 확인하였다.